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From: David Woodhouse <dwmw2@infradead.org>
To: Peter Zijlstra <peterz@infradead.org>,
	Paolo Bonzini <pbonzini@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	linux-kernel@vger.kernel.org, Dave Hansen <dave.hansen@intel.com>,
	Ashok Raj <ashok.raj@intel.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Andi Kleen <ak@linux.intel.com>,
	Arjan Van De Ven <arjan.van.de.ven@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Asit Mallick <asit.k.mallick@intel.com>,
	Jason Baron <jbaron@akamai.com>
Subject: Re: [PATCH 06/24] x86,kvm: Fix indirect calls in emulator
Date: Thu, 25 Jan 2018 09:49:13 +0000	[thread overview]
Message-ID: <1516873753.30244.34.camel@infradead.org> (raw)
In-Reply-To: <20180125093453.GX2228@hirez.programming.kicks-ass.net>

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On Thu, 2018-01-25 at 10:34 +0100, Peter Zijlstra wrote:
> On Wed, Jan 24, 2018 at 11:43:05AM +0100, Paolo Bonzini wrote:
> > 
> > On 24/01/2018 11:35, Peter Zijlstra wrote:
> > > 
> > > On Tue, Jan 23, 2018 at 08:48:13PM +0000, David Woodhouse wrote:
> > > > 
> > > > On Tue, 2018-01-23 at 21:28 +0100, Borislav Petkov wrote:
> > > > > 
> > > > > 
> > > > > > 
> > > > > >        flags = (flags & EFLAGS_MASK) | X86_EFLAGS_IF;
> > > > > > -     asm("push %[flags]; popf; call *%[fastop]"
> > > > > > -         : "=a"(rc) : [fastop]"r"(fop), [flags]"r"(flags));
> > > > > > +     asm("push %[flags]; popf; " CALL_NOSPEC
> > > > > > +         : "=a"(rc) : [thunk_target]"r"(fop), [flags]"r"(flags));
> > > > > Oh, "thunk_target" is magical.
> > > > You can use THUNK_TARGET(fop), which will be "rm" on 32-bit and avoids
> > > > register starvation in some cases (I don't think the hyperv calls
> > > > worked until I did that).
> > > The reason I didn't use THUNK_TARGET() was exactly because it used "rm"
> > > and the current code did "r" only. I'm happy to change if people can
> > > agree on something ;-)
> > In practice, "fastop" is going to be in a register because of how it's
> > computed, but "rm" is okay.
> OK, so the other occurence in that file uses "+S", which is the SI
> register. That cannot use THUNK_TARGET(), right?
> 
> So do you want one THUNK_TARGET and one open coded, or keep the patch as
> is (both open coded) ?

As long as it builds for i386, you might as well keep them both open-
coded. The "rm" was there mostly for the hyperv call, which ran out of
registers completely when it was just "r".

This patch *really* wants to be going to Linus urgently as a retpoline
fix, and not buried as patch 6/24 though, right? Likewise 7/24? 

Both of them,

Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>

... unless you want me to send them on, but it makes most sense for
Thomas to round them I suspect?



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  reply	other threads:[~2018-01-25  9:49 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-23 15:25 [PATCH 00/24] objtool: retpoline and asm-goto validation Peter Zijlstra
2018-01-23 15:25 ` [PATCH 01/24] objtool: Use existing global variables for options Peter Zijlstra
2018-01-23 15:25 ` [PATCH 02/24] objtool: Add retpoline validation Peter Zijlstra
2018-01-23 18:21   ` Borislav Petkov
2018-01-26  9:54   ` David Woodhouse
2018-01-23 15:25 ` [PATCH 03/24] x86/paravirt: Annotate indirect calls Peter Zijlstra
2018-01-25 10:02   ` David Woodhouse
2018-01-25 10:22     ` Peter Zijlstra
2018-01-25 10:26       ` Juergen Gross
2018-01-25 10:52         ` David Woodhouse
2018-01-25 11:35           ` Peter Zijlstra
2018-01-26  9:57             ` David Woodhouse
2018-01-29 17:58   ` Josh Poimboeuf
2018-01-29 18:09     ` David Woodhouse
2018-01-29 18:17     ` Peter Zijlstra
2018-01-29 18:38   ` Josh Poimboeuf
2018-01-29 19:21     ` Peter Zijlstra
2018-01-30 16:02       ` Josh Poimboeuf
2018-01-31  4:13         ` [PATCH] x86/paravirt: Remove 'noreplace-paravirt' cmdline option Josh Poimboeuf
2018-01-31  5:59           ` Juergen Gross
2018-01-31  9:42           ` [tip:x86/pti] " tip-bot for Josh Poimboeuf
2018-01-23 15:25 ` [PATCH 04/24] x86,nospec: Annotate indirect calls/jumps Peter Zijlstra
2018-01-26 10:19   ` David Woodhouse
2018-01-29 17:44     ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 05/24] x86: Annotate indirect jump in head_64.S Peter Zijlstra
2018-01-26 10:24   ` David Woodhouse
2018-01-23 15:25 ` [PATCH 06/24] x86,kvm: Fix indirect calls in emulator Peter Zijlstra
2018-01-23 20:28   ` Borislav Petkov
2018-01-23 20:48     ` David Woodhouse
2018-01-24 10:35       ` Peter Zijlstra
2018-01-24 10:43         ` Paolo Bonzini
2018-01-25  9:34           ` Peter Zijlstra
2018-01-25  9:49             ` David Woodhouse [this message]
2018-01-26 10:57             ` Paolo Bonzini
2018-01-23 15:25 ` [PATCH 07/24] x86,vmx: Fix indirect call Peter Zijlstra
2018-01-25  9:36   ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 08/24] x86,sme: Annotate " Peter Zijlstra
2018-01-26 10:37   ` David Woodhouse
2018-01-29 17:49     ` Peter Zijlstra
2018-01-29 17:50       ` Peter Zijlstra
2018-01-31  9:29     ` Peter Zijlstra
2018-01-31 15:04       ` Josh Poimboeuf
2018-01-31 16:00         ` Peter Zijlstra
2018-01-23 15:25 ` [PATCH 09/24] jump_label: Add branch hints to static_branch_{un,}likely() Peter Zijlstra
2018-01-24 18:46   ` Borislav Petkov
2018-01-23 15:25 ` [PATCH 10/24] sched: Optimize ttwu_stat() Peter Zijlstra
2018-01-23 15:25 ` [PATCH 11/24] x86: Reindent _static_cpu_has Peter Zijlstra
2018-01-23 15:25 ` [PATCH 12/24] x86: Update _static_cpu_has to use all named variables Peter Zijlstra
2018-01-25 19:31   ` Borislav Petkov
2018-01-23 15:25 ` [PATCH 13/24] objtool: Implement base jump_assert support Peter Zijlstra
2018-01-26 10:45   ` David Woodhouse
2018-01-23 15:25 ` [PATCH 14/24] x86: Add a type field to alt_instr Peter Zijlstra
2018-01-23 15:25 ` [PATCH 15/24] x86: Annotate static_cpu_has alternative Peter Zijlstra
2018-01-23 15:25 ` [PATCH 16/24] objtool: Implement jump_assert for _static_cpu_has() Peter Zijlstra
2018-01-23 15:25 ` [PATCH 17/24] objtool: Introduce special_type Peter Zijlstra
2018-01-23 15:25 ` [PATCH 18/24] objtool: More complex static jump implementation Peter Zijlstra
2018-01-23 15:25 ` [PATCH 19/24] objtool: Even more complex static block checks Peter Zijlstra
2018-01-23 15:25 ` [PATCH 20/24] objtool: Another static block fail Peter Zijlstra
2018-01-29 22:52   ` Josh Poimboeuf
2018-01-30  9:56     ` Peter Zijlstra
2018-01-31  3:12       ` Josh Poimboeuf
2018-01-31 10:01         ` Peter Zijlstra
2018-01-31 10:07           ` David Woodhouse
2018-01-31 10:27             ` Peter Zijlstra
2018-01-23 15:26 ` [PATCH 21/24] objtool: Skip static assert when KCOV/KASAN Peter Zijlstra
2018-01-23 15:26 ` [PATCH 22/24] x86/jump_label: Implement arch_static_assert() Peter Zijlstra
2018-01-23 15:26 ` [PATCH 23/24] x86: Force asm-goto Peter Zijlstra
2018-01-23 15:26 ` [PATCH 24/24] x86: Remove FAST_FEATURE_TESTS Peter Zijlstra
2018-01-23 15:42 ` [PATCH 00/24] objtool: retpoline and asm-goto validation Peter Zijlstra
2018-01-23 15:57   ` David Woodhouse
2018-01-23 16:03     ` Peter Zijlstra

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